Publikationen
Es wurden 4 Publikationen gefunden
Tapia Armijos, M.F.; Homeier, J.; Espinosa, C.; Leuschner, C. & de la Cruz, M. (2015): Deforestation and Forest Fragmentation in South Ecuador since the 1970s – Losing a Hotspot of Biodiversity. PLos ONE 10(9), e0133701.
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DOI: 10.1371/journal.pone.0133701
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Abstract:
Abstract:
Deforestation and fragmentation are major components of global change; both are contributing to the rapid loss of tropical forest area with important implications for ecosystem functioning and biodiversity conservation. The forests of South Ecuador are a biological 'hotspot' due to their high diversity and endemism levels. We examined the deforestation and fragmentation patterns in this area of high conservation value using aerial photographs and Aster satellite scenes. The registered annual deforestation rates of 0.75% (1976–1989) and 2.86% (1989–2008) for two consecutive survey periods, the decreasing mean patch size and the increasing isolation of the forest fragments show that the area is under severe threat. Approximately 46% of South Ecuador's original forest cover had been converted by 2008 into pastures and other anthropogenic land cover types. We found that deforestation is more intense at lower elevations (premontane evergreen forest and shrubland) and that the deforestation front currently moves in upslope direction. Improved awareness of the spatial extent, dynamics and patterns of deforestation and forest fragmentation is urgently needed in biologically diverse areas like South Ecuador.
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Keywords: |
South Ecuador |
deforestation |
fragmentation |
Curatola Fernández, G.F.; Obermeier, W.A.; Gerique, A.; López Sandoval, M.F.; Lehnert, L.W.; Thies, B. & Bendix, J. (2015): Land Cover Change in the Andes of Southern Ecuador - Patterns and Drivers. Remote Sensing 7(3), 2509-2542.
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DOI: 10.3390/rs70302509
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Abstract:
Abstract:
In the megadiverse tropical mountain forest in the Andes of southern Ecuador, a global biodiversity hotspot, the use of fire to clear land for cattle ranching is leading to the invasion of an aggressive weed, the bracken fern, which is threatening diversity and the provisioning of ecosystem services. To find sustainable land use options adapted to the local situation, a profound knowledge of the long-term spatiotemporal patterns of land cover change and its drivers is necessary, but hitherto lacking. The complex topography and the high cloud frequency make the use of remote sensing in this area a challenge. To deal with these conditions, we pursued specific pre-processing steps before classifying five Landsat scenes from 1975 to 2001. Then, we quantified land cover changes and habitat fragmentation, and we investigated landscape changes in relation to key spatial elements (altitude, slope, and distance from roads). Good classification results were obtained with overall accuracies ranging from 94.5% to 98.5% and Kappa statistics between 0.75 and 0.98. Forest was strongly fragmented due to the rapid expansion of the arable frontier and the even more rapid invasion by bracken. Unexpectedly, more bracken-infested areas were converted to pastures than vice versa, a practice that could alleviate pressure on forests if promoted. Road proximity was the most important spatial element determining forest loss, while for bracken the altitudinal range conditioned the degree of invasion in deforested areas. The annual deforestation rate changed notably between periods: ~1.5% from 1975 to 1987, ~0.8% from 1987 to 2000, and finally a very high rate of ~7.5% between 2000 and 2001. We explained these inconstant rates through some specific interrelated local and national political and socioeconomic drivers, namely land use policies, credit and tenure incentives, demography, and in particular, a severe national economic and bank crisis.
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Keywords: |
Ecuador |
remote sensing |
Andes |
fragmentation |
land cover change |
bracken fern |
deforestation drivers |
Landsat |
image pre-processing |
attractors of landscape change |
Werner, F.A.; Köster, N.; Kessler, M. & Gradstein, S.R. (2011): Is the resilience of epiphyte assemblages to human disturbance a function of local climate?. Ecotropica 17, 15-20.
Werner, F.A. & Larrea, M.L. (2010): Response of vascular epiphyte diversity to different land-use intensities in a neotropical montane wet forest. Forest Ecology and Management 260, 1950-1955.
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DOI: 10.1016/j.foreco.2010.08.029
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Abstract:
Abstract:
Although vascular epiphytes contribute substantially to the biodiversity of tropical montane forests, it is
unclear how their diversity and community composition is affected by forest alteration. We studied the
response of vascular epiphyte assemblages to different intensities of land-use in a montane wet forest of
northeastern Ecuador: (1) unmanaged mature forest; (2) mature forest with mid- and understorey opened
for cattle grazing; and (3) isolated remnant trees in cattle pastures. The numbers of individuals and species
of epiphytes per host tree did not differ significantly between land-use types, neither did total epiphyte
species richness (n = 30 trees). However, total species richness of pteridophytes was significantly lower on
isolated remnant trees compared to unmanaged forest, whereas several taxa rich in xerotolerant species
(Bromeliaceae, Orchidaceae, Piperaceae) exhibited the opposite trend. An analysis of floristic composition
using ordination (NMS) and randomisation techniques (MRPP) showed that epiphyte assemblages on
isolated remnant trees were significantly distinct from unmanaged forest while managed forest was
intermediate between those two vegetation types. Ordination analysis further indicated reduced floristic
heterogeneity in disturbed habitats. These results suggest considerable, rapid species turnover since
land-use change 6 years prior to study, with pteridophytes being replaced by more xerotolerant taxa.
We attribute this floristic turnover primarily to changes in microclimate towards higher levels of light
and desiccation stress associated with forest disturbance. Our results support the notion that community
composition offers a more sensitive indicator of human disturbance than species richness.
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Keywords: |
land-use change |
human disturbance |
microclimate |
deforestation |
beta diversity |
fragmentation |
isolated trees |
secondary forest |
species richness |
species turnover |